Do multipurpose companion trees affect high value timber trees in a silvopastoral plantation system?

Establishment of native timber trees on deforested land may contribute to the livelihood of farmers, to improved ecosystem services and to increased greenhouse gas uptake. Here, we present a new silvopastoral planting design to assess species performance and interspecific competition or facilitation effects among native timber and multipurpose trees in Central America. Two timber species, Tabebuia rosea and Cedrela odorata, were established in three low-density planting regimes allowing combined tree and future livestock production: (1) solitary planting, (2) companion planting with Guazuma ulmifolia, and (3) companion planting with the nitrogen-fixing Gliricidia sepium. We quantified survival, growth and reforestation potential of the two timber species subjected to the different planting regimes for the first 2 years after establishment. Nitrogen concentration as well as stable nitrogen and carbon isotope composition (δ¹⁵N, δ¹³C) of leaves of the timber saplings were determined. T. rosea showed higher survival and better growth than C. odorata under varying environmental conditions (soil, concomitant vegetation). Performance of the timber saplings was unaffected by either companion species. Planting regimes had no effect on foliar nitrogen concentration and δ¹⁵N of the two timber species, although δ¹⁵N values indicated nitrogen fixation activity in G. sepium trees. Planting regimes affected foliar δ¹³C values in T. rosea. δ¹³C values were significantly higher in solitarily growing individuals, suggesting lower exposition to water stress conditions in saplings surrounded by companion species. As we found positively correlated growth traits among timber and multipurpose trees, a combined planting may benefit farmers by providing additional goods and services.     

Tree–grass interactions for N in Nothofagus antarctica silvopastoral systems: evidence of facilitation from trees to underneath grasses

Nothofagus antarctica forests in south Patagonia are usually used as silvopastoral systems but how grasses and trees compete for specific resources, such as nitrogen in these systems is unknown. To understand interactions between grasses and N. antarctica trees for N, an experiment with ¹⁵N labeled fertilizer was carried out comparing N absorption by grasses growing under trees (silvopastoral system) with an open site. Labeled ¹⁵NH ₄ ¹⁵ NO₃ fertilizer at 10 % atom excess was added in spring at both sites and ¹⁵N was measured in herbage, soil and trees every 30 days during the growing season. Soil was the component that containing the greatest amount of N and greatest ¹⁵N recovery. Grasses growing in the silvopastoral system absorbed almost double of the fertilizer applied than grasses in the open site (32.4 kg N ha^?1derived from fertilizer based on ¹⁵N recovery). Roots were also an important fate for N absorbed, representing 50 and 63 % of total ¹⁵N recovered in grass roots of open and silvopastoral sites, respectively. Trees absorbed 69 % less applied N than grasses in the silvopastoral system; being mainly allocated in small branches, sapwood and fine roots. Overall, ¹⁵N recovery was 65 % higher in the silvopastoral system (tree + grasses) than in the open site (grasses). Silvopastoral system made more efficient use of the ¹⁵N added. These results indicated that N. antarctica trees in the silvopastoral system may “facilitate” fertilizer N absorption of grasses by improving environmental conditions like water availability or by reducing competition for inorganic N between soil microorganisms and plants.     

An evaluation of farmers’ experiences planting native trees in rural Panama: implications for reforestation with native species in agricultural landscapes

In the Republic of Panama, reforestation with native species is of great interest, but many landholders often do not participate in tree planting projects and little information exists about landholder interest in, or experiences with, native trees. This study evaluates the experiences of farmers participating in a native species reforestation initiative in rural Panama to identify lessons learned that can guide on-going or future tree planting efforts. Based on the results of a questionnaire administered to program participants and non-participants (n = 68), we found that trees are important to farmers for multiple reasons, primary a variety of environmental and economic benefits. No relationship between the size of landholdings or land tenure status and the desire to plant trees was found. All participants in the program considered their experience to be positive, few had problems with their plantations, and most were interested in planting more native trees. The program’s frequent and ongoing technical support was an important factor for farmers. These results indicate widespread interest in, and success with, planting native species and underscore the need to systematically examine farmers’ interests and perceptions when planning, implementing, and evaluating reforestation initiatives.     

Insights from full-rotation Nelder spacing trials with Eucalyptus in São Paulo,Brazil

The choice of spacing among trees for operational plantations is typically based on one or more experimental plantations that test for the response of tree and stand growth to a range of tree-to-tree distances. The most common design for spacing experiments entails rectangular plots that test different distances between rows, and between trees within rows, and with replication of plots covering one to several hectares within a single stand. Other designs may offer more information with simpler layouts, and we examined the insights that could be obtained from a Nelder (fan-shape) design, where spacing among trees varies with the radial distance from a central point. The response of Eucalyptus dunnii seed-origin trees to spacing was essentially similar between a classic plot design replicated in four blocks (tree spacing from 4.5 to 9.2 m² tree^?1, covering 1.4 ha of land), and a Nelder design (tree spacing from 2.1 to 44.0 m² tree^?1, covering 0.6 ha of land). The Nelder design showed slightly higher volume increment through 10 years of stand development than the block design (for the range of overlap in spacing), but the treatment effect of spacing was essentially identical between the designs at the level of both trees and stands. A second Nelder experiment used clonal-origin trees from six clones, testing for differences in responses to spacing among clones. In all three spacing experiments and for all clones, individual-tree growth was greatest at the widest spacing and stand-level growth was highest at the tightest spacing. These trends were much clearer across the wider range of spacing tested in the Nelder plots (228 to 4 760 trees ha^?1) than in the narrower range of spacing tested in the block design (1 111 to 2 222 trees ha^?1). Current annual increment reached a higher, earlier peak at narrow spacing. At 8.5 years, the light use efficiency (stem volume growth per unit of light intercepted) was about twice as great for trees at narrow spacing than at wider spacing. Overall, the Nelder designs provided the same information on responses to spacing as the classic block design. The simplicity and small size of Nelder designs provide valuable insights for basic decisions on spacing for operational plantations, particularly when forestry extends into new geographic areas, new genotypes, and new silvicultural techniques.     

Effects of intercropping systems of trees with soybean on soil physicochemical properties in juvenile plantations

The intercropping system of tree with soybean in juvenile plantations, as a short-term practice, was applied at Lao Shan Experimental Station in Mao’er Shan Forest of Northeast Forestry University, Harbin, China. The larch (Larix gmelinii)/soybean (Glycine max.) and ash (Fraxinus mandshurica) intercropping systems were studied in the field to assess the effects of the intercropping on soil physicochemical properties. The results showed that soil physical properties were improved after soybean intercropping with larch and ash in one growing season. The soil bulk density in larch/soybean and ash/soybean systems was 1.112 g·cm⁻³ and 1.058 g·cm⁻³, respectively, which was lower than that in the pure larch or ash plantation without intercropping. The total soil porosity also increased after intercropping. The organic matter amount in larch/soybean system was 1.77 times higher than that in the pure larch plantation, and it was 1.09 times higher in ash/soybean system than that in the pure ash plantation. Contents of total nitrogen and hydrolyzable nitrogen in larch/soybean system were 4.2% and 53.0% higher than those in the pure larch stand. Total nitrogen and hydrolyzable nitrogen contents in ash/soybean system were 75.5% and 3.3% higher than those in the pure ash plantation. Total phosphorus content decreased after intercropping, while change of available phosphorus showed an increasing trend. Total potassium and available potassium contents in the larch/soybean system were 0.6% and 17.5% higher than those in the pure larch stand. Total potassium and available potassium contents in the ash/soybean system were 56.4% and 21.8% higher than those in the pure ash plantation. Biography: FAN A-nan (1972–), female, Ph. Doctor in Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China.     

Establishing evaluation index system for desertification of Keerqin sandy land with remote sensing data

科尔沁位于我国东北部,地处东北平原向内蒙古高原的过渡地带(42°41'-45°15'N,118°35'-123°30'E),是受荒漠化影响较重的地区。利用外业调查数据,依据地表形态和生态状况的变化,确定了植被盖度、裸沙地占地百分比和土壤质地3 项评价指标,并建立了基于遥感的科尔沁沙质荒漠化评价指标体系,其中裸沙地占地百分比用混合像元分解的方法获得。利用外业调查的数据对该指标体系进行验证,结果表明该指标体系适于研究区域的荒漠化评价。表4参11。     

Selection of mixed-effects parameters in a variable–exponent taper equation for birch trees in northwestern Spain

Context

Taper equations predict the variation in diameter along the stem, therefore characterizing stem form. Several recent studies have tested mixed models for developing taper equations. Mixed-effects modeling allow the interindividual variation to be explained by considering both fixed-effects parameters (common to the population) and random-effects parameters (specific to each individual).

Aims

The objective of this study is to develop a mixed-effect variable exponent taper equation for birch trees in northwestern Spain by determining which fixed-effects parameters should be expanded with random-effects parameters.

Methods

All possible combinations of linear expansions with random effects in one and in two of the fixed-effects model parameters were tested. Upper stem diameter measurements were used to estimate random-effects parameters by the use of an approximate Bayesian estimator, which calibrated stem profile curves for individual trees.

Results

Parameter estimates for more than half of the mixed models investigated were nonsignificant. A first order autoregressive error structure was used to completely remove the autocorrelation between residuals, as mixed-effects modeling were not sufficient for this purpose.

Conclusion

The mixed model with the best fitting statistics did not provide the best calibration statistics for all upper stem diameter measurements. From a practical point of view, model calibration should be considered an essential criterion in mixed model selection.     

Growth Parameters and Nutrient Content in Four Multipurpose Tree Species with Potential Characteristics for Agroforestry Systems in a Cerrado Region in Botucatu,São Paulo State,Brazil

Abstract

In order to evaluate growth characteristics, adaptability, biomass production, nutrient recycling, nutrient distribution and the ability to regenerate degraded land, a trial using four multipurpose tree species (Leucaena leucocephala, Leucaena diversifolia, Acacia melanoxylon and Mimosa scabrella) was undertaken over two years in a distrophic red yellow latosol (oxisol) following a randomized block experimental design with four replications.

At the age of two years, A. melanoxylon and L. diversifolia were the tallest species (5.25 and 4.97 m, respectively) and A. melanoxylon and M. scabrella had the largest diameters at 20 cm from tree base.

Mimosa scabrella and A. melanoxylon had the highest dry matter production and quantity of nutrients in the above ground biomass. In all species, the highest nutrient contents were found in the leaves, followed by branches and stems. From all species, the highest Nutrient Utilization Efficiency Indexes were obtained for sulphur, phosphorous, and magnesium; L. diversifolia was the most efficient for nitrogen, potassium, calcium, sulphur, and manganese, while A. melanoxylon was the most efficient for phosphorus, magnesium, boron, iron, and zinc. Litter production levels over a three month period were as follows: M. scabrella > A. melanoxylon > L. diversifolia > L. leucocephala. Litter nutrient content was higher in M. scabrella than in the other species.     

Examination of the failure behavior of wood with a short crack in the radial–longitudinal system by single-edge-notched bending test

The failure behavior of wood with a short crack was examined by conducting the single-edge-notched bending tests of a radial-longitudinal system on Agathis specimens. In the test, the mode I critical stress intensity factor was measured, and its validity was checked by the result from double cantilever beam testing method. The mode I critical stress intensity factor decreased when the crack length approached zero. With crack length correction, a constant critical stress intensity factor was obtained over a wide range of crack length including crack-free specimen.     

Water harvesting in a ‘runoff-catchment’ agroforestry system in the dry lands of Ethiopia

A major production constraint in arid and semiarid areas of Ethiopia is a lack of water for crop growth. Run off water can be harvested by channeling it into micro- catchments (MC) where it slowly infiltrates into the soil. The increased moisture provides more plant growth in these dry lands. An experiment using MC was conducted in eastern Ethiopia to study the growth of four multipurpose tree species intercropped with grass. Trees and grass were grown in 25 m² and 100 m² MC. Plant height, root collar diameter, and mortality rate of trees were determined 12 months after planting. Dry matter yield of grasses and trees were measured and nutrient analysis of plant tissues was determined. In a separate experiment the biomass of trees was determined after 2.5 years of continuous growth without grass competition. Soil moisture, organic matter, texture and bulk density of the soils were also determined. Mean tree height was 10% greater in the 100 m² than in the 25 m² MC. Root collar diameter and survival rate showed similar increase with 13% and 7.8% respectively. Acacia saligna and Leucaena leucocephala showed better growth in both plot sizes than the indigenous Acacia seyal and Acacia tortilis. The dry matter yield of grass (Panicum maximum) was over 12 tons/ha and 8 tons/ha in the 100 m2 and 25 m2 plots respectively. Soil moisture content was greater in MC than in control plots with no water harvesting structures with 31% and 24% during the wet and dry seasons respectively. The use of water harvesting can improve fodder production and carrying capacity of the dry lands of Ethiopia.     

Incorporation and remobilization of ¹³C within the fine-root systems of individual Abies alba trees in a temperate coniferous stand

Forest ecosystems have a large carbon (C) storage capacity, which depends on their productivity and the residence time of C. Therefore, the time interval between C assimilation and its return to the atmosphere is an important parameter for determining C storage. Especially fine roots (≤2 mm in diameter) undergo constant replacement and provide a large biomass input to the soil. In this study, we aimed to determine the residence time of C in living fine roots and the decomposition rates of dead fine roots. Therefore, we pulse-labelled nine 20-year-old individual silver fir trees (Abies alba Miller; ～70 cm tall) with 13CO? in situ to trace the assimilated C over time into the fine-root systems. Whole trees were harvested at different time points after labelling in autumn, biomass was determined and cellulose and starch of fine roots were extracted. Moreover, soil cores were taken and ingrowth cores installed, in which fine roots were genetically identified, to assess incorporation and remobilization of 13C in the fine roots of silver fir trees; litterbags were used to determine fine-root decomposition rates. The 13C label was incorporated in the fine-root system as cellulose within 3 days, with highest values after 30 days, before reaching background levels after 1 year. The highest δ13C values were found in starch throughout the experiment. 13C recovery and carbon mean residence times did not differ significantly among fine-root diameter classes, indicating size-independent C turnover times in fine roots of A. alba trees of ～219 days. Furthermore, carbon was remobilized from starch into newly grown fine roots in the next spring after our autumn labelling. One year after installation, litterbags with fine roots revealed a decrease of biomass of ～40% with relative 13C content in fine-root bulk biomass and cellulose of ～50%, indicating a faster loss of 13C-labelled compounds compared with bulk biomass. Our results also suggest that genetic analysis of fine-root fragments found in soil and ingrowth cores is advisable when working in mixed forest stands with trees of similar fine-root morphology. Only then can one avoid dilution of the labelling signal by mistake, due to analysis of non-labelled non-target species roots.     

Dependence of dispersion on vegetation density in a tidal creek‐mangrove swamp system

The dependence of dispersion in a tidal creek on the vegetation density in a fringing mangrove swamp is discussed through a numerical model. A secondary circulation prevails everywhere in the tidal creekmangrove swamp system and is generated by the overflow into the swamp at every high tide. As a result, dissolved and suspended matter moving with the circulation is trapped in the swamp for a fraction of the tidal cycle; it flows out of the swamp at ebb tide and disperses in the creek. The relation between the dispersion coefficient and the mangrove vegetation density is shown to be nonlinear. Dispersion is large both for bare and high vegetation densities and minimum for intermediate vegetation density. The ecological and management applications may be profound as our study suggests that such systems may be unstable and cannot naturally recover from excessive anthropogenic disturbances.     

Why and where do adult trees die in a young secondary temperate forest? The role of neighbourhood

? The density and identity of tree neighbourhood is a key factor to explain tree mortality in forests, especially during the stem exclusion phase.

? To understand this process, we built a logistic model for mortality in a spatially explicit context, including tree and neighbourhood predictors. Additionally, we used this model to build mortality risk frequency distributions. Finally, we tested this model against a random mortality model to predict the spatial pattern of the forest.

? Annual mortality rate was high for pedunculate oak (Quercus robur, 6.99%), moderate for birch (Betula celtiberica, 2.19%) and Pyrenean oak (Q. pyrenaica, 1.58%) and low for beech (Fagus sylvatica, 0.26%). Mortality risk models for pedunculate oak and birch included stem diameter, tree height, canopy position and neighbourhood. Mortality was affected by the specific nature of the neighbourhood showing a clear competitive hierarchy: beech > pedunculate oak > birch. Models based on random mortality and logistic regression model were able to predict the spatial pattern of survivors although logistic regression predictions were more accurate.

? Our study highlights how simple models such as the random mortality one may obscure much more complex spatial interactions.

     

Developments in Swedish forest policy and administration – from a “policy of restriction” toward a “policy of cooperation”

Abstract

New tools and forms of cooperation at the landscape level are needed in order for forestry and environmental conservation to co-exist in areas with many land owners. Awareness has existed for several years in Sweden that cooperation at the landscape level is essential for protecting areas of high environmental value. This awareness has come to expression in several projects and initiatives. One of these projects is the Östra Vätterbranterna Partnership, a successful example of the new orientation toward environmental management as formulated in the government bill Sustainable protection of nature areas: new working methods with a focus on collaboration and increased dialog by involving more actors and utilizing a greater combination of steering instruments. This development resonates with the growing trend toward deregulation and less state intervention in environmental management, implying a stronger emphasis on new governance structures and market-driven processes. This paper examines the preconditions for a development toward governance-oriented forms of steering in the area of environmental policy and law, with specific emphasis on the protection of forestry areas with high environmental value. Paralleling this development, the transformation of environmental public administration is analyzed, using a model representing three different perspectives on administration's role, values and meaning, showing state action's progressive transition from “rowing” to “steering” to “serving” and facilitating.     

Afforestation with ‘multipurpose trees’ in ‘media lunas’, a case study from the Tarija basin,Bolivia

Human-induced soil erosion has already affected all of the potential farming land in the Tarija basin/South Bolivia. It is described as an afforestation method involving media lunas and multipurpose trees, whose implementation is associated with a high degree of mobilization of the target group.On sites where a sufficient number of media lunas have been established, surface runoff is drastically reduced. They diminish the risk of failure of newly planted trees during frequently occurring dry phases, and promote their growth by preventing excessively large fluctuations in the soil-water balance and increasing soil moisture in general. Mostly indigenous multipurpose trees (Acacia and Prosopis) serve to stabilize erosion-prone sites on a long-term basis, and become invaluable because they provide a source of firewood, improve the soil, and yield protein-rich livestock forage during dry season. Media lunas provide more favorable conditions for natural vegetation.     

Establishment of a transgenic system in fast-growing black locust （Robinia pseudoacacia L.）

The AhDREB1 gene, cloned from Atriplex hortensis L., was transferred into black locust （Robiniapseudoacacia L.） by an Agrobacterium-mediated transformation. The results suggest that stems of black locust sub-cultured in vitro for 20 d are suitable for genetic transformation. The optimum concentrations of kanamycin and cefotaxime were 30 and 150 mg.L-1, respectively. Important factors affecting the transformation efficiency were studied by means of a L9（3^4） orthogonal design. An effective system for genetic transformation in black locust was developed as follows： the stems were pre-cultured for 2 d, immersed in the Agrobacterium solution （OD600 = 0.7） with 10 mg·L^-1 acetosyringone for 21 min and then co-cultured for 2 d. The selection pressures, changing from low to high, could improve transformation efficiency. The transgenic plants were identified by a PCR method. The PCR results indicated that the AhDREB1 gene had been integrated into the genome of black locust and two lines of the transgenic plants were obtained.     

Freedom with what? Interpretations of “responsibility” in Swedish forestry practice

Responsibility is a key aspect of all regulation, and forest regulation is no exception. How should responsibility be understood and used in a time characterized by complexity and uncertainty? This paper develops a typology that distinguishes six notions of responsibility and then employs it in analyzing interpretations of responsibility in Swedish forestry practice. The Swedish forest management system is a deregulated system structured by the governing principle of “freedom with responsibility.” By investigating how responsibility is understood and enacted by forest consultants and forest owners, we demonstrate the practical fluidity of the responsibility concept. We emphasize the need for an understanding of responsibility that fosters sensitivity and adaptiveness to external issues and actors in the face of uncertainty, and identify obstacles in current forestry policy and practice to enacting such an understanding.